Exam Question

(a) Describe the effect of cavitation on (6)

(i) The thrust and torque

(ii) The propeller blades

(b) A ship of 355190 tonne displacement is 325 m long, 56 m wide and floats in sea water of density 1025 kg/m3 at a draught of 22.4 m. The propeller has a diameter of 7.4 m, a pitch ratio of 0.85, and when rotating at 1.5 rev/s the real slip is 48.88% and the fuel consumption is 165 tonne per day. The Taylor wake fraction Wt, Wt=0.5Cb-0.05. Calculate: (10)

(i) The ship speed in knots

(ii) The reduced speed at which the ship should travel if the fuel consumption on a voyage is to be halved

(iii) The length of the voyage if the extra time on passage is six days when travelling at the reduced speed

(iv) The amount of fuel required on board before commencing on the voyage at the reduced speed.